Current missile fuzing systems typically utilize RF (radar) optical (infrared) sensors to detect missile proximity to an airborne target and to detonate the missile warhead at the opportune point in the missile trajectory to maximize the damage inflicted on the target. Unfortunately such proximity fuzing systems are susceptible to being prematurely triggered by natural effects, such as rain, snow, clouds and sun, and, in the case of low level targets such as helicopters, by clutter produced by water waves, terrain promontories, and salvo effects. In addition, these proximity fuzing systems can be "spoofed" by countermeasures effected by the target. RF sensors can be jammed electronically, and optically sensors can be confused by flares. The results are either no warhead detonation or detonation outside the target kill range.
To minimize proximity fuzing system malfunction due to these various effects, it is known to utilize an onboard timer which is preset prior to missile launch to delay or "both" system activation and/or enablement until the missile is in close engagement with an airborne target. This approach, however, requires some form of data link with the missile, typically a hard wire, to permit presetting the timer just prior to launch. This data link complicates the fuzing system electronics, increases cost, and reduces reliability.
As another approach to minimizing the sensitivity of proximity fuzing systems to natural effects and target countermeasures, it has been proposed to use electrostatic sensors to detect target proximity. See, for example, Ziemba et al., U.S. Pat. No. 4,291,627, issued Sept. 29, 1981. As is well known, the outer surface of any airborne target becomes electrostatically charged while in flight through the atmosphere due to the effects of air friction and engine ionization. Thus, detection of the electric field closely surrounding an airborne target can provide a means for detecting the proximity of an attacking missile to an airborne target. See, for example, Krupen U.S. Pat. No. 4,183,303, issued Jan. 15, 1980. Since this inherent electric field can not be readily recreated in disassociated relation to the target, electrostatic fuzing system sensors are not susceptible to being foiled by target countermeasures. Moreover, electrostatic sensors are not influenced by ground clutter, as, for example, during terrain-hugging trajectories to engage low-flying targets, such as helicopters.